Six-freedom degree articulated flexible COMERO high precision calibration method

Abstract

A six-DOF high-precision calibrating method for an articulation type coordinate measuring machine comprises the following steps of: using the articulation type coordinate measuring machine as a calibrated machine, using a three-coordinate measuring machine with higher precision as a standard machine, and disposing the calibrate machine into the measurement space of the standard machine; respectively obtaining the standard coordinates of probes in a standard coordinate system and the measurement coordinates of the probes in a calibrated coordinate system; using the standard coordinates and the measurement coordinates as sampling data, and obtaining the error parameter of the calibrated machine with least square method. The method is characterized in that the sampling density is that each joint of the calibrated machine at least locates at two equally divided angle positions in each circle (360 DEG), and the placement attitudes of the calibrated machine formed by the combination of the six joints with different angle positions are at least 64 types. The inventive method can further improve parameter identification precision, and improve the entire precision of the measuring machine.

Description

technical field [0001] The invention belongs to the technical field of coordinate measurement, and in particular relates to a calibration method for an articulated flexible coordinate measuring machine. Background technique [0002] The articulated flexible coordinate measuring machine usually consists of each measuring arm connected in series with each rotating joint (joint for short) to form an open-chain structure, and the end of the open-chain structure is the measuring head of the measuring machine. Each joint can rotate around its own axis. In order to record the angle of joint rotation, an angle sensor needs to be installed on the joint. As an angle sensor, a high-precision circular grating is one of the choices. Each joint has one degree of freedom, and a six-degree-of-freedom articulated flexible coordinate measuring machine has six joints. When using a measuring machine for coordinate measurement, the coordinates of the measuring machine probe are a function of th...

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Problems solved by technology

[0005] Although the above-mentioned existing calibration methods can realize parameter identification, they have defects in sampling strategies: "Research on Calibration Technology of Flexible Three-coordinate Measuring Arm" (Journal of Xi'an Jiaotong University, 2006.3, pp284-286) (hereinafter referred to as Document 1 ) The sampling strategy adopted in ) is "evenly select 12 points in the working space of the measuring arm"; "Structure System and Error Correction Calibration Analysis of Flexible CMM" (Tool Technology, 2006.40, pp76-78) (hereinafter referred to as Document 2) does not give a specific sampling strategy; while "Parameter Identification Method of Joint-Type Flexible Coordinate Measuring Machine" (Journal of Agricultural Machinery, 2007.7, pp129-132) (hereinafter referred to as Document 3) adopts the method of single-point conical dimple Calibration method, fix a cone dimple at a position in the measurement space, and use an articulating flexible coordinate measuring machine to continuously sample 200 points for the apex of the cone dimple

In the actual calibration process, it is also found that the effect of calibration is better in a certain interval of space, which can make the whole machine achieve higher accuracy, and the effect of the whole machine in another interval is poor.

In this way, if the measurement interval is inconsistent with the calibration interval, the actual accuracy of the measuring machine is not high.

[0006] In addition, due to the randomness of sampling in the existing calibration methods, the sampling density is not enough. For example, it is recorded in Document 1 that "select 12 points evenly in the working space of the measuring arm", but this is far from enough; 3. Fix a cone at a position in the measurement space, and use an articulated flexible coordinate measuring machine to continuously sample 200 points at the apex of the cone. Such a point cannot represent the performance of the joint-type coordinate measuring machine in the entire measurement space; This reason leads to unsatisfactory calibration results. The outstanding problem is that the calibration in a certain spatial area cannot guarantee the accuracy of actual measurement in other spatial areas.

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